The present invention concerns a machine for producing herringbone-pleated structures from sheet material in which alternating transverse folds made along parallel ridge lines are connected together by alternating longitudinal folds. Such structures are particularly useful in the manufacture of filter elements.
Pleated structures of this type can be made to achieve a great variety of forms and can, for example, comprise broken or undulated ridge lines which are in principle, identical and equidistant. Each of these breaks or undulations is connected to that of the preceding ridge and the following ridge by a small longitudinal fold, or a small undulation in the case of undulated ridges. It will be noted that all of these small folds, or small undulations, are alternately concave and convex and reverse themselves as they pass from one ridge to the next.
The machines used in the past for the production of such structures have never given complete satisfaction, either because they are very complicated and hence very costly, or else because their efficiency has been low and resulting in high production costs.